In an aircraft or in a vehicle, such as a train, bus or the like, there is a demand to arrange as many seats for passengers as possible. Hence, usually, the passenger seats are provided with the maximum number being arrayed relative to a width-wise size of an aircraft body (fuselage) or vehicle body.
In case of an aircraft, for example, if an outer diameter of the body is 115 inches (292.1 cm) or so, four seats arrayed in the width direction of the body can be arranged in rows in the length-wise direction of the body. But, in this case, if the outer diameter is less than 106 inches (269.2 cm), for example, no sufficient width of each seat or of a passage (aisle) can be ensured and arrangement of the four seats becomes physically difficult. Thus, conventionally, as shown in FIG. 7, in an example of an aircraft having a body 1 of an outer diameter less than 106 inches (269.2 cm) (the 328 type jet plane of Fairchild Dolnier Company, for example), three seats 2 are arranged in array in the width direction, that is, two rows of seats on one side and one row of seats on the other side with a passage therebetween are arranged.
In designing bodies of various vehicles including aircrafts, trains, buses, etc., it is sought that as many seats as possible are to be arranged in the limited space, as mentioned above. On the other hand, comfortability of passengers sitting on the seats must be ensured. If too many seats are arranged, the space for each of the seats becomes narrow so that the comfortability will be damaged.
For example, as shown in FIG. 8(a), an example in which seats 2 of four rows can be physically arranged relative to a body 1 is considered. In such case, even if the seats 2 can be physically arranged in four rows, if a width of each of the seats 2 or width of an arm rest (that is, an interval between adjacent two seats 2) is small, adjacent passengers will make contact with each other on their shoulders. If the width of the seat 2 or arm rest is thus made larger, a width of a passage 5 becomes narrow and movement of passengers or crew in the vehicle will become difficult.
In order to make both of the width of the seat 2 or arm rest and the width of the passage 5 as larger as possible, it is preferable to move the level of a floor 3 to around a vertical directional central position of an approximate circular cross sectional shape of the body 1. But if the level of the floor 3 is lifted too much, the space between the floor 3 and a ceiling of the body 1 will become too narrow and there is a limitation to do so.
Hence, if a sufficient width of the passage 5 and seat 2 is to be ensured with the comfortability of passengers being importantly considered, it will be the only way to make an outer diameter of the body 1 larger, as shown in FIG. 8(b).
But if the outer diameter (or cross sectional area) of the body 1 is made larger, it directly leads to an increase of aerodynamic drag of the aircraft. If the aerodynamic drag increases, in order to fly at the same velocity, a larger engine thrust will be needed and this will become a large obstruction for energy saving.
Hence, especially in the aircraft, in order to increase the number of seats as many as possible while the body is made as small as possible and the passenger comfortability is ensured as much as possible, there are many restrictions that make the realization thereof difficult.